Accelerator for the vulcanization of rubber



Patented May 17, 1932 UNITED STATES PATENT OFFICE ADRIEN CAMERON, OF MONTREAL, QUEBEC}, CANADA, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO THE ZROIESSHEAR, &

TION OF DELAWARE HASSLACI-IER CHEMICAL COMPANY, A CORPORA- ACCELERATOR roR THE ,VULGANIZATION OF RUBBER No Drawing. Original application filed January 20, 1926, Serial No. 82,613, and in Germany lanuary 19, 1927. Divided and this application filed March 28, 1928. Serial No. 265,524.

The object of this invention is to provide a substance for aiding the vulcanlzation of rubber which will be cheap while at the same time powerful, rapid and nonpoisonous. A

5 further object isto provide in this same substance a material which will retard the aging of the finished rubber. This application is a division of my copending application S. N. 82,613 issued April 8, 1930, as U. S. Patent 1,754,100.

My invention comprises an improved product formed by the condensation of aliphatic aldehydes having a plurality of C atoms with aromatic amines in the presence of an acidic catalyst and includesa process of treating rubber or similar material with this improved aldehyde amine condensation product and vulcanizing the rubber. My invention also includes the product of the process. One species of this material is claimed in an application S. N. 82,612 filed by me of even date herewith and issued March 10, 1931, as U. S. Patent 1,796,240.

The condensation productsof aldehydes glomerate on standing. A recently suggested process is a secondary treatment of these soft materials with a further aldehyde addition after a primary condensation has been effected.

I have found that such further aldehyde additions are unnecessary and a waste. In

my U. S. Patent 1,562,146 of Nov. 17, 1-925, I

have disclosed and claimed one method of preparing improved condensation products of aldehydes and amines and one application ofthis process as the formation of an imand aromatic amines have been used in vari.

proved acetaldehyde-aniline condensation product.

I have now discovered a new process of preparingimproved aldehyde-aromatic amine condensation products. I have found that it is'possible to obtain a hard product suitable for use as an accelerator of vulcanization of rubber condensing, for example, aniline and acetaldehyde in the presence of acid catalysts., This new product can be ground to a fine powder and will not agglomerate after grindingrit has excellent accelerating properties and greatly extends the lifeo'f the rubber article in which itisu'sed.

In general I havefound that all acidic materials will produce the accelerators of my invention. Preferably I use small amounts of an acid zinc salt, such as zinc chloride, as the catalystor zinc chloride first to securea primarycondensation and finally a mineral acid, such as hydrochloricacid, to complete the condensation. I have also used hydrochloric acid alone but then the condensation 2 reaction isquite violent and the mass tends to boil up. due to the-steam liberated by the heatofthe reaction. I have secured similar results with other acids and salts of which sulphuric acid, dinitro-chlor-benzoli and aluminum chloride are'examplesi The salts used are acidic, i. e;they givean acid reaction in water solution. It is generally conceded in the art that the presence of appreciable amounts of acids in the rubber will retard vulcanization. The accelerators prepared by myprocess though made with acid catalysts do not add an appreciable acidity to the rubber. First, because such small amounts of accelerator are used in proportion to therubher and secondly, because only small amounts of acid catalysts are required in the condensation to form the accelerator. V

7 It hasbeen proposed to prepare various rubber compounding materials such as age resis tors, accelerators and conditioners from aldehydes and amlnes n aqueous acid solutions.

In these, however, large amounts of acid are present and this not only alters the course of the reaction and produces a difierenttype of product but also serves with the water to dissolve out certain constituents of the mix.

salt, suchas zinc chloride, and a"mineralacidg" such as hydrochlonc 3.(31Cl, 111 success on, as

catalysts in the aldehyde-amine condensation reaction whereintwo moles of the aldehyde are used to eachgmole of the amine. I preferably first prepare a catalyst consisting ;ofan addition product of zinc chloride and the amine by mixing these in react- -ing propor tions. A smallamount of this .zinc chloride-amine product is thenadded to the amine to-be condensed in a jacketed. kettle, with-thorough stirring to prevent the zinc-chloride-amine: from settling out. Cooling water is now circulated in-the kettle jacket-7 andthe aldehyde .(slight excess over the. 2 molecular ratio to care for any vaporization loss), is run into the kettle; the pressure in-the-kettle is allowed to rise to about 10 pounds; and the aldehyde addition regulated'to maintain: a= slight pressure. The

pressure drops to near zero in about 15 minutes after the aldehyde has been added. A

: small amount of: aqueous hydrochloric acid solution is now added: in a periodof 10-15 minutes, with stirring continued as before. Goolingwat'er is still-being circulated.

Dueto the catalytic effect'upon a-ddi'ngthe acid the kettle temperature rises sharply,

reaching about 80-85 C. As soon-as this temperature begins to fall showing a completion of the major part of the reaction, the coolingwater is shut-off and the water jacket emptied. Thus theheatof the reaction is utilized as fully as'possible and serves to carry the reaction to completion.

- charge is stirred for about 30 minutes longer and then blown: out intopanstocool. WVhen a single catalyst suchas zin'c chloride ordinitro-chlor-benzol isiused the process starts with this catalyst present in1the amine. In,

some cases I have found the reaction stubb'orn-to start; I thenhea't the batch with steam and the-reaction will proceed as before. Some single catalysts require I more time to complete'the-reactionthanmy double "catalysts given above or'again some aldehydes and amines are slower to react. Here it is'necessary to keep up the final temperatime with steam till tests indicate that the desired result has been attained. Simple tests of hardnessor color. will determine this with sufiicient accuracy.

The

Example I 51.5 pounds aniline (1 mole) 50.0 pounds acetaldehyde (2 moles slight excess) f j V 0.22-pounds zinc chloride-aniline 0.25 pounds HCl (in aqueous solutiOIl) i i The, materials were reacted as indicated above and gave a hard, brown product having a-softening point of about 80 'C. (For method:of testingsoftening point see Allens Commercial Organic Analysis, fourth edition VolUIIL-pages 76-77)..

Vvhenused as the accelerator in the formula: 1 v v 100 parts by weight smoked sheet, 51 parts byweight zinc oxide,-5 parts-by weight sulphur, l part by weight accelerator, and-cured at a temperature corresponding 'to that of steam at 4L0'pounds pressure the following" results were obtained} 7 Elonga- Load at 7007 i Time of cure mom I e1ong Load at break minutes 9. 5 1900 lbs/in 28201bs./in. m nutes 9. 0 1700 lbs/in. BASOIbs/in. muiutesh 9.0 2600 lbs/in. 3880 lbs/in. mmutes 9. 1 3200 lbs/in. 3880 lbs/in. minutes; 7 9.0 2300 lbs./in. 2701 lbs/in.

Example I l When used as the accelerator in'the rub-- ber formula of Example I and this cured for 30Ymi nutes at 40 pound steam temperature a tensile strength of 3193 lbs. /in. was obtained with an elongation of 9.7

V I vE'wample [II 181 gramsxylidine v130 grams acetaldehyde 2.0 grams zinc chloride 1.5 grams HCl' (n25% aqueous solution) Thesecomponents were reacted as inthe previous case. Theproduct was a hard dark matrgial with a: softening point of about 75 Tested'as the accelerator in the rubber'formula of Example I and'this cured 30 minutes at 40 pound steam temperature it gave a tensile strength of 3686 lbs/in. with anelongation of 9.3. I

A hard product was obtained after heating at 95100 C. for 1 hour.

\Vhen tested as the accelerator in the rubber mix of Example I and cured for 30 minutes at the temperature of 40 pound steam a tensile strength of 3090 lbs/in. was obtained with an elongation of 10.

Example V 250 grams crotonaldehyde 165 grams aniline 0.8 grams zinc. chloride aniline 1.6 grams HCl (in aqueous solution) These components were react-ed as in II and heated for 1 hour at 95 (3., this resulted Ewample VI 400 grams aniline 380 grams acetalclehyde 6 grams zinc chloride The zinc chloride was first added to the aniline and the acetaldehyde then run in; the reaction mixture was then heated at about 80 C. for 15 minutes. A hard product resulted which was tested as the accelerator in the rubber formula of Example I and cured for minutes at the temperature of pound steam a tensile of 3304: lbs/in. and an elongation of 9.3 resulted.

I have found that the products prepared as above not only are good accelerators of the vulcanization of rubber but they also impart to the rubber very excellent aging properties. The present theory in the art is that the aging of rubber in use is largely due to an oxidizing action of theair on the rubber. From this standpoint those substances which tend to preserve the rubber, that is, improve its aging qualities have been designated as anti-oxidants.

The excellent aging properties of a' rub' Load at break Days aged 3266 lbs/in. 3392 lbs/in. 3303 lbs/in. 3341 lbs/in) 3135 lbs/in. 3155 lbs/in. 3398 lbs/in. 3449 lbS./in.

Samples of rubber for Example I were subjected to the oxygen bomb test. This consisted in treating the specimens at C. with oxygen at .300 pounds per square inch pressure. The results were as follows Hours in the bomb Load at break 33251bs.lin. 31251bs./in. 2625 lbs/in.

This shows excellent aging properties since it has been shown that 10 hours in a bomb under the above conditions is approximately equivalent to one year of natural aging (Bie)rer and Davis Ind. Eng. Chem. Aug. 1925 The age resisting qualities are further brought out in a second bomb test. The rubber for this test was prepared from:

Partghlgy W91 Smoked sheet 100 Zinc oxide 5 Sulphur 5 Acceleratonanti-oxidant of Ex. I 3

Cured at temperature of steam at 40 lbs. /in. for 30 minutes. Specimens of the rubber were then aged in a vbomb at 60 C. in an,

Hours in the bomb Load at break 3100 lbs/in. 3100 lbs/in. 3150 lbs/infi The age resisting qualities of this rubber has been increased by a slight increase in the amount of accelerator-anti-oxidant.

The materials cited above as catalysts namely znclg, H2804. A101 are not by any means the only materials which give excellent results according to the procedure described, but are given as examples of the wide diversity'of acidic materials which when used in the proportions specified in aldehyde amine condensation reactions and in the substantial absence of water, catalyze the formation of accelerators which are also anti-oxidants. I therefore wish the term acidic catalyst to be construed broadly in the appended claims.

Whether the catalytic eflect shown in my experiments is due to the acidic substances per se, or to the addition products of these acidic substances with the amines is immaterial as influencing the scope of this invention. Nor do I wish to be limited to any exact proportions of catalyst or reacting components given above. The use ofthe acidic catalysts in preparing resin type accelerators admits of the widest application.

What I claim is 1. A process which comprises condensing under essentially anhydrous conditions a straight chain aliphatic aldehyde having a .lpluralityof-c arbonatoms withaiprimaryiaromaticamine ill'l :the ipresence of an acidic materlal as a catalyst .and WlthOLlt a solvent.

2. A process which comprises condensing lunder essentially anhydrous :conditions two moles of a straightchain aliphatic aldehyde having a plurality of-carbon atoms with one .hyde with one mole of aniline in the presence of'zinc chloride and hydrochloric acid as a catalyst.

5. A'process whichcomprises partially condensing under essentially anhydrous conditionsa straight chain aliphaticaldehyde'ha-ving a plurality of carbon atoms with I a primary aromatic amine and then addingan acid material thereto andrfurther reacting the mixture :to complete said aldehyde-amine condensation: and without asolvent.

6. A process which comprises partially :conden-sing two moles of :a straight chain aliphatic aldehyde havinga plurality of car- I 'bonatoms with one .mole of a primary aromaticamine in the presence of an acid salt andthen addlng a secondacidmaterial thereto and further reacting the -mixture to; complete said aldehyde-amine condensation while maintaining substantially anhydrous conditions throughout the process and without a solvent.

7. A process which comprises partially condensing two moles of crotonaldehydewith one mole of aniline in the presence of an acid salt and then adding a second acid vmaterlal thereto andfurther reacting the mixture tocomplete said aldehyde-amine condensation while maintaining substantially anhydrous conditions throughout the process and with out a solvent.

8. A process which comprises partially condensing two moles of crotonaldehyde with one mole of aniline in the presence of zincchloride and then adding hydrochloric acidthereto and further reacting the mixture to complete said aldehyde-amine condensation while maintaining substantially anhydrous conditions throughout the process and without a solvent.

9. A process which comprises partiallycondensing-two moles of crotonaldehyde with one mole ofzaniline' inthe presence of Zinc chloride and then adding hydrochloricacid thereto and further reacting the mixture to complete said aldehyde-amine condensation said condensation reaction beingcarriedout :inlth'eabsence of substantialamounts of water beyond that formed'inithe:reaction.

10. Anew composition of jmatter consist 'ing of the condensationzproduct produced by adding :zinc rchloride 'to aniline and allowing crotonaldehyde .to react therewith while maintaining substantially anhydrous conditions throughout the process and without a solvent. 5'

11. A composition of matter-consisting of the condensation product obt'ained by reacting under substantiallyanhydrous conditions and without a solvent a straightchain aliphatic aldehyde havingaplurality or" carbon atoms and a primaryzaromatic amine lin the presence of up to 5% by weight of auzacid cataly'stmaterial, said productretaining.said catalyst :material.

.12. A-composition of matter consisting of thecondensation product obtained by react ing under substantially anhydrous conditions and without a solvent a-straight chain aliphatic aldehyde having a plurality of carbon atoms and a primary aminein the;presence of an acid salt, saidqproduct retaining said salt. 7

13. A c'ompos'ition of'matter consisting of the condensation product obtained by Ereacting under sub tantially anhydrous -conditionsrand without a-solvent a straight chain alphatic 1 aldehyde :having a plurality oi1carbon atoms and atprimar-yaromatic aminein the presence otup toz5%by-weight of:anacid salt catalyst material=for the condensation reaction, said productretaining said salt.

14. .A product comprising :a "condensation product obtained by reacting under substantiallyanhydrous conditions witii'out a solvent astraig'ht chainaliphaticaldehyde having a plurality of carbon'atomsand a primary-aromatic :amine in the presence ofa zinc-salt said product retaining said salt.

'15. A product comprising a condensation product obtained .by reacting under substantially anhydrous conditions and without a solvent two moles of crotonaldehyde with one mole of aniline inzthe presence'of up-to 5% by Weight of zinc chloride said product retaining said zinc chloride.

16. A new composition ofma'ttcr consisting ofthe condensation product producedby adding zinc-chloride to aniline and allowing acetaldehyde to react therewith while maintaining substantially anhydrous conditions throughout theprocess and without a solvent.

17. A product comprising a condensation product obtained by reacting under substantially anhydrous conditions and without a solvent two mols'of acetaldehydc'with onemol of aniline in the presence of up to 5% by weight of zinc chloride,.said product retaining said zinc chloride.

Signed at Montreal, Quebec, Canada, this 12th-day of .March, A. D. 11928.

p AD-RIEN CAMERON. 

